Stabilizing apparatus



Oct. 15, 1935. N. MINORSKY STABILIZING APPARATUS Filed A ril 11, 1932 W T W6 #vymrom Oct. 15, 1935. N. MINORSKY STABILIZING APPARATUS Filed April 11, 1932 v6 Sheets-Sheet 2 Mam Oct. 15, 1935. N. MINORSKY STABILIZING APPARATUS Filed April 11, 1932 6 Sheets-Sheet 3 FIG. 3.

Oct. 15, 1 935.

' N. MINORSKY STABILIZING APPARATUS Filed April 11, 1952 6 Sheets-Sheet 5 Patented a. 15, 1935 UNITED STATES PATENT OFFlCE 40 Claims.

This invention relates to improvements in apparatus for anti-rolling stabilization of ships, airships, submarines and other moving vehicles hereinafter broadly designated as ships or vessels, by means of displacement of liquid ballast between a pair, or sets of pairs, of tanks placed on both sides. of the vessel. The liquid ballast referred to may be water, oil, mercury, or any other fluid which for convenience hereafter will be designated broadly as water or liquid.

More specifically the invention relates to improvements in the so called active method of anti-rolling stabilization, in which the displacements of the liquid ballast are controlled by externally applied forces or pressures, such as air pressure from a blower or compressor driven by an auxiliary source of power, or in the case of heavy liquids such as mercury, by hydraulic systems such as rams actuated by oil or the like, or other means for effecting the transfer of water, as later described. It is known that such active method or principle applied to control the displacements of the ballast distinguishes from the earlier so called passive methods in which the displacements of water were produced by the angular motion. of the ship without any actuation on the part of an external source of power.

The movement of water in such passive tank system is substantially in time quadrature with respect-to the motion of the ship when the roll- I ing is produced by substantially regular trocholdal waves. The roll quenching efliciency of an anti-rolling system of this kind under the above specified conditions is comparatively good especially when the tank system has its own period sufliciently near to the point of synchronism of the ship and of the waves whereby the dynamical head necessary for the acceleration of water between the tanks can be continuously supplied by the potential head available from the'fact that the ship is rolling and that, for this very reason, instantaneously one tank is higher than the other.-

It is apparent that the performance of the passive tank stabilizer depends essentially on the fact that the 'ship is rolling over substantial angles at which the potential head is sufficient for the acceleration of water athwartships in the proper time and ,to the required extent. For this reason anti-rolling tank passive systems never quench the rolling to a substantially negligible degree but merely damp out or reduce the excessive roll to somewhat smaller amplitudes.

Furthermore the roll quenching efliciency of the passive tank system decreases still further when the rolling ceases to be regular and when consequently the above mentioned mutual compensation of potential and dynamical heads is no longer possible; in some cases owing to com- 5- plicated conditions of phase reversal occurring in a confused irregular sea the passivetank system as is observed, may even enhance the rolling instead of quenching it.

The disturbing moment applied to the ship 10 from the waves generally speaking is never regular. Subsequent waves differ from each other both in length, period and shape, and for this reason, the rolling is never a periodic or recurrent phenomenon. l5

Complicated conditions of phase reversal above referred to are frequently observed which leads either to development of flat spots in the rolling curve or to angular accelerations of the ship considerably in excess of those which would 20 otherwise occur if the rolling were regular, corresponding to a substantially trcchoidal profile of the waves.

The existing tendency both in naval and merchant ship design is to build vessels with a considerable metacentric height in order to secure a greater inherent safety of ships. Such ships, however, are generally bad rollers insofar as their roll has not only a considerable magnitude but generally is very irregular thus reflecting similar irregularity of the waves encountered,

Vessels having a comparatively small metacentric height are not safe at sea especially when in a damaged condition, but they generally roll more in their own period and are not influenced by the irregularities of the sea to the same extent as the vessels with a great metacentric height.

In view of these facts the anti-rolling tank system on modern vessels must be adapted to operate essentially under the conditions of irregular rolling which is generally encountered at sea, whereas the regular rolling is rather a rare exception.

It is the fundamental object of this invention to provide a new method and means for an efflcient control of displacements of water between stabilizing or anti-rolling tanks either actually by transfer or effectively without direct transfer, as will be explained, in such manner as to provide the maximum roll quenching in all cases, that is, 60 both for the regular and irregular rolling, and to render the tank system' considerably more efllcient to the extent of securing substantially dead heat stabilization.

Stabilization according to this system, is ac- The rolling of vessels among waves, as is known, 'is expressed approximately by the following differential equation due to Wm. Froude. I 0 d9 d9 2 1r I +m +lx +Wh6-Wh Sin (1) Where I is the effective moment of inertia of the ship about the longitudinal axis of symmetry passing through the center of avity,

K1 and K2 are coefiicients of resistance to rolling,

W is the displacement,

h is the metacentric height,

5 is the maximum eflective'wave slope,

T1 is the apparent'period of the waves,

9 is the instantaneous angle of rolling.

In this equation the left member characterizes the ship and the right one the action of the waves. If this latter is erratic, clearly the harmonic second member cannot be used to represent such erratic condition.

As a starting point for this exposition I adopt a method of control in which the instantaneous excess w of the liquid ballast on one side of the vessel and hence the instantaneous value of the stabilizing moment Mt exerted by the tanks on the ship about its longitudinal axis, is made substantially proportional to the instantaneous angular velocity of rolling, so that at any moment there exists an instantaneous relation where K is another coefilcient of proportionality which can be made considerably greater than the coeflicient K1 of natural so called wave making resistance to rolling, due to the form of the hull, bilge keels and the like.

The diiferential Equation (1) in this case acquires a new coeflicient of the term with an dt namely, K =K1+K inal K1 and it can be shown by analysis that the damping action of such control will be considerably enhanced, which will. favorably affect the wiping out of the free oscillation of the ship from time to time arising in the seaway, as well as to reduce the efl'ect 01' the external disturbances due to waves, whether regular or erratic. In view of the fact that the new coeflicient K is considerably greater than the original K1; the second coeflicient K: can.be neglected in Equation (1) applied to the stabilizer of this kind. It is apparent, that viewed from this angle, everything will happen in a manner as if the vessel, while being sub- Jected to exactly the same sequence of disturbing actions and of exactly the same magnitude, were placed insteadofinwateninahighly viscous or much greater than the origdamping substance such as thick molasses, heavy lubricating gear grease, and the like. One conceives readily that all actions coming'from the waves, whether regular or erratic would be equally damped out and would have no appreciable efl'ect I in producing rolling.

- If the variation of gravity on the waves, gen erally small for modern vessels, is neglected, the moment Mt is proportional to the excess 10 of water instantaneously situated on the rising side 10 of the vessel. The preceding condition (2) in this case is equivalent to the following:

15 that is the instantaneousexcess w of water at all 7 times must be in time phase with angular velocity of rolling and must be situated on the rising side of the ship. The factor of proportionality or cou pling a is established by the design and in general must be subject to variation in order to adjust its value to each individual case.

If the preceding theoretical condition (2) of damping is differentiated one has:

Equations (3) and (4) follow directly from (2) and conversely Equation (3) can be obtained by integrating (4) with respect to the time and Equation (2) is also obtained by integrating (3) with respect to the time and determining in both cases the constants of integration by suitable initial conditions. Equation (2) determines directly the law of variation of the liquid weight which accounts for roll quenching. It is diflicult, however, to produce an equipment capable of concentrating considerable masses of water in proportion to the instantaneous angular velocity of the ship especially when the rolling is irregular in view of the inertia of the liquid, and also on account of the time lags in the controlling system.

It is more practical to produce the instantane- 5o ous rate of transfer dw F? (2), quite irrespective of the i'act whether the 65 rolling is regular (or harmonic) or entirely irregular. On this principle as a base this invention utilizes means for regulation of the rate of transfer of the ballast substantially in proportion to, or as a function of, the instantaneous angular 70 acceleration of the ship both in direction and in magnitude. For illustrative p rposes the rate of transfer is made substantially portional to the angular acceleration in the following description. 76

, In view of the fact that the angular acceleration 4 of the ship is in phase with the disturbing moment the rate of transfer of the liquid is controlled substantially in proportion to the value of this moment both in direction and magnitude; the control of this kind for this reason responds to, or compensates for the very disturbing cause producing the rolling instead of reacting upon the actual rolling, which is the efiect of the disturbing moment above referred to.

Conversely, if the timing of the transfer takes place in accordance with Equation (3) the integrated value of this transfer, that is the moment exerted by the tanks owing to the excess; of water in one of them, is in phase with the instantaneous angular velocity of rolling as is necessary for emcient roll quenching. The problem, therefore, consists in establishing a predetermined, preferably linear, relation between the angular acceleration of the 'vessel and the rate of transfer of the liquid, whether such transfer is direct or only effective.

To this end I provide an instrument continuously responsive to angular acceleration of the ship, which by means of an electrical circuit, or circuits having also continuous characteristics, modifies the conditions of operation of the power plant displacing the liquid. in such manner that the rate of transfer of water is continuously maintained substantiallyin proportion to the instantaneous angular acceleration of the vessel, both in direction and magnitude. This following up of the angular acceleration on the part of the rate of transfer in practice takes place inevitably with a certain time lag due partially to the inertia of water and partially to inherent time lags inthe various instruments, circuits and apparatus.

To obviate this I provide an additional controlling circult responsive to the rate of angular acceleration or, which is equivalent, to the third time derivative dt v of the angular motion of {rolling The physical significance of the third jtime derivative is the rate of change of the resultant torque applied to the ship from the waves.

when, therefore, the angular acceleration varies, the corrective control by the third time derivative compensates for the time lags and produces an anticipatory action whereby the rate of flow l l alt is varied substantially in accordance with Equation (3) and hence the excess amount (or weight) w of water concentrated instantaneously on the rising side of the vessel by this very fact is varied in accordance with Equation (2) as is required for an eflicient roll quenching.

Equation (40' indicates also that the acceleration of flow 1: alt must be proportional to the third derivative of .this excess 1002)) rolling? In order to accelerate the water flowing between the tanks a certain additional accelerational head is required,vhence the Equation (4) indicates that this additional head must be controlled in response to the rate at which the ex- 5 ternal torque of the waves varies at each particular instant.

. Conversely the accelerational head accelerating the flow of water athwartships between the tanksis varied in accordance with Equation (4) m the control of the rate of flow in accordance with Equation (3) can be produced with a'considerabledegree of accuracy insofar as the major part of the time lag due to the inertia of water is compensated in this manner. 15

The preceding considerations are altogether general and applicable to the regular as well astothe irregular orierratic disturbances.

I havershown in my co-pending U. S. patent application 'Ser. No. 544,651 that in the most 20 general case. the stabilizing moment necessary for the compensation of any kind of disturbing action coming either from waves or wind should contain-theoretically a plurality of higher time derivatives, so that in the instant case when the 25 excess of water 10, considered as a function of time, is controlled by the instruments, the most general relation is of the form:

- 2 W(# )=W( o)+A so 6 dt t whereby the correct amount of the water at a given instant of time to-l-At can be concentrated on the rising side of the ship if the amount of as well as the values of the subsequent time derivatives at the preceding instants (to) is instrumental in producing the controlling action, as this is apparent from Equation; (5) representing Taylors expansion.

Each subsequent higher time derivative of motion-responsive instrument or controlling apparatus corrects the resultant action of the plurality of the precedingones and improves the timing of stabilizing moment whereby for the same amount of water in the tanks a greater roll quenching action is produced.

In the present invention the rate of transfer diof water is made proportional to the angular acceleration, the acceleration of the transfer is made proportional to the rate of angular acceleration Equation (6) shows that the value of angular velocity 2? can be correctly computed at a subsequent instant' to+At which can be designated conventionally as the present instant" if the value of angular velocity at the preceding instant to, which may be called also conventionally the past instant is supplemented by the plurality of high time derivatives a a ar an all relative to the past instants.

The controlling actions emanating from the instruments relate inevitably to the past instants in view of the time lags, and relations and (6) being interdependent show that the presence of high time derivatives permits of eliminating the effect of time lags and produces a dynamically correct concentration of the water ballast at the instant to+At if its concentration was correct, that is fulfilling Equation (2), at the preceding instant to. Equations (5) and (6) are altogether general, applicable to all kinds of functions whether harmonic, periodic or entirely irregular, as long as they are continuous and admitting derivatives which is always the case in dynamics. In other words, once the ballast has started quenching in accordance with Equation (2) it will never get out of step with the disturbance, whether regular or irregular. These broad dynamical considerations will be more apparent from the latter analysis of performance of the stabilizing system forming the subject of this invention when quenching an irregular rolling.

In order to produce the control of the ballast of this kind the instruments and the circuits according to this invention control the rate of flow substantially in proportion to the value of angular acceleration of the ship and the acceleration of this fiow substantially in proportion to the rate of acceleration of the ship. The excess of the ballast concentrated instantaneously on the rising side of the vessel is then obtained by the process of integration with respect to time without any additional instruments. As in all processes of integration a cumulative error is possible; in the present instance this error would manifest itself in a slow drift of the liquid ballast to one side of the ship whereby the stabilization would occur, instead of about the true upright or vertical position, about a slightly inclined position in space. It is true that the inherent stability of the vessel will tend to eliminate this slow drift of the liquid ballast to one side. I prefer, however, to provide an ,additional controlling means responsive either-to a slow average departure of the ship from verticalityor to a point of relative quiescence of the ship among waves which equalizes continuously in the first case and instantaneously and discontinuously in the second case this cumulative error or drift whereby the stabilizing efficiency of the dynamical control operating in accordance with Equations (2), (3) and (4) remains undisturbed.

. When the equipment is started among the waves either from rest or from the passive performance I prefer to introduce the active stabilization gradually by varying the coupling coefiicient a. by suitable variation of parameters of controlling circuits whereby the liquid ballast is accelerated with gradually increasing amplitudes. In cases when the rolling is excessive and the Equations (2) (3) and (4) cannot be fulfilled the invention provides automatic discriminating means responsive to the excess of rolling and decreasing the intensity of the coupling coefllcient so as to avoid violent surges or rushes of water between the tanks, assuming, of course, that the power capacity of the prime moves is very high.

Broadly stated the invention consists in the provmion of a method and means for producing the rate of variation of the stabilizing moment due 6 to the tanks in a predetermined functional relation to the angular motion of rolling, whereby under all circumstances the basic condition of optimum roll quenching given by Equation (2) is continuously fulfilled. In the case in which 10 the tanks are connected by a channel or pipe the above mentioned control of the rate of variation of the stabilizing moment is identified with the control of the fiow of water through this channel in a predetermined functional relation to the 16 angular motion of rolling. Of particular importance is the application of this broad principle to the case of irregular erratic rolling.

In summing up the salient objective points of this invention one" can state as follows:

1. The velocity of the fiow is continuously controlled in response to the angular acceleration of the ship. v

2. The acceleration of the flow is continuously controlled in response to the rate of angular acceleration of the ship.

3. Cumulative error inherent to integration of the flow is eliminated by an equalizing system operatively associated with the periods of relative quiescence.

4. Adjustability of the stabilizing system to meet on various ships, different conditions of stabilization or on the same ship to meet different conditions of navigation, at various times, is produced by a continuous change of operative association between the fiow of the liquid ballast and the instruments responsive to angular movement of rolling. I

Other features and advantages of this invention can be better understood from the following de- 4,0 scription in connection with the accompanying drawings.

In the accompanying drawings forming part of this description:

Fig. 1 represents a transverse vertical section partially in elevation, showing one form of the stabilizing system,

Fig. 2 represents a top plan of the same partially in section, i

Fig. 3 represents a side elevation of one form of the inertial instrument or accelerom'eter with part of its associated control,

Fig. 4 represents a fragmentary enlarged elevation, partially broken away, of the velocity of flow responsive follow up system, 66

Fig. 5 represents a top plan of the arrangement shown on Fig.. 4,

Fig. 6 represents a fragmentary enlarged detail of the control device shown on Fig. 3,

Fig. 7 represents a wiring diagram of control 59 circuits of one form of the invention,

Fig. 8 represents a partial wiring diagram of a modified control system of duplicate systems as applied to the port side of the ship only with some associated parts and a modified form of accelerometer ditically illustrated,

Fig. 9 represents a complete wiring diagram of the form of invention shown on Fig. 8, of duplicate systems, and as applied only to the port side 70 of the ship,

Fig. 10 represents a diagram of an equalizing valve system relating to air pressure transfer systems.

Fig. 11- represents a side elevation partially in '16 section of a form of the invention embodying animpeller control of the water transfer,

Figs. 12 and 13 represent diagrammatic fragmentary sections respectively, partially in plan and elevation of the ship with an outboard noncommunicating tank,

Fig. 14 represents a graph of relative phases of the ships irregular rolling and a series of diagrams of the stabilizing performance of the tanks in a series of successive time intervals.

Fig. 15 represents a similar graph and diagram incident to regular rolling and illustratively associated with the impeller control of Fig. 11, and

Fig. 16 represents a fragmentary vertical sec- 15 tion partially in elevation of an automatic heavysea-protective device of a pair of devices.

Referring to Fig. 1, 2 and 3 are port and starboard tanks respectively fitted' into the ship t is a cross connecting channel (or channels) be- 20 tween the tanks. As one form or embodiment of the invention for transferring water between the tanks I show a means for applying and using the pressure of air generated by a compressor blower or any similar device, but I wish it to be understood that other means and methods .for such actuation can be used in connection with the control system forming the subject of this invention as particularly pointed out and claimed later herein. 5 is a blower either of, the so-called positive or centrifugal, or any other type.

The output of the blower is connected to the tanks 2 and 3 by means of pipes 'l, 8 shown partially in cross section. The suction of the blower is connected to the tanks by the pipes I0 and H substantially as shown.

For the purpose of a better efiiciency of the plant, I propose to connect simultaneously the output of the blower to one tank, say 3, and. the suction to the other, say 2, reversing connections every half a 40 period of the roll or any time when this reversal is needed as will be shown later on. Stream line shaped valves l2, I3, Hi mounted for controlled substantially axial movements in the respective pipes by means of streamlined links or arms I5, I6,

l1, l8, l9, 20, 2| and 22, respectively, mounted for free oscillation on stuffing box axes, so as to either open, amplify or close or regulate the passage of the air substantially as shown, and are attached to control levers 25, 26, 21 and 28 which are also stream line shaped inside the pipes and rotatably mounted about stufiing box axes 29, 30, 3| and 32 perpendicular to the drawing'of Fig. 2 and supported-by brackets on the outside of the pipes near the spherical enlargement of the pipes required for location of the valves.

The levers 25, 26 are connected to the rod 35 and the levers 21, 28 to the rod 35, said rods being mounted for a limited longitudinal displacement necessary for partially or completely opening or an closing the valves. The rods 35 and 35 are guided by means of guides 31, 36, 39, 46 and are connected to sleeves 42, 43 suitably guided for longitudinal motion and prevented from rotating by guides 23 and 24 respectively. The sleeves 42 and 5 63 are internally but oppositely threaded and respectively engage the appropriately threaded screws 43, 45 fixed to worm wheels 46, M, respectively. The last mentioned wheels are in engagement with the worm 48 directly connected to 70 the armature H8 of a separately excited direct current follow up motor 56. It is apparent from the foregoing description that when the motor 50 rotates the rods 35 and 36 move in opposite directions and operate the valves substantially as 75 shown. Fig. 2 shows the extreme left position of the rod 35 and the extreme right position of the rod 36; as seen on the figure the valve 12 is wide open and the pressure of the blower is applied to the water in the starboard tank 3.- At the same time the valve I3 is open and the port tank 2 is 5 connected with the suction side of the blower. Simultaneously valves l4 and II are closed. The water level in the starboard tank is lowered, whereas in the port tank the level rises, in accordance with, or accompanied by, the flow of 10 water through the communicating channel l.

The rotation of the pilot motor 50 in the opposite direction reverses the conditions just described; the rod 35 is moved to starboard and the rod 36 to port which closes valves l2 and I3 and opens valves 15 H and it. The water in the starboard tank rises and in the port tank goes down. Intermediate conditions of pressure occur for the intermediate position of the control rods 35' and 35. It is seen that the reactions of the air streams on the valves 20 are balanced so that the force required to displace the control rods is rather small, and the pilot motor 50 is a very small motor in comparison with the constant speed motor 6 driving the blower. Furthermore the load on the main motor 25 6 is substantially constant owingto the differential operation of the valves.

From the foregoing description it is apparent that the difierence of pressures in the tanks is a certain function of the relative displacement of 30 the rods and hence of the number of revolutions of the motor 5|! from its central position when all four control levers 25, 26, 21 and 28 and associated valves are so disposed that the pressures in both tanks are equal. 5

The control of the follow up motor 50 will now be described. --In order to produce a rate of fiow in the connecting pipes which is proportional to the instantaneous angular acceleration of the ship, I prefer to employ the inertial instrument or accel- 40 erometer 5|, shown separately on Fig. 3 and also indicated on a smaller scale on Fig. 1. This form of accelerometer or modifications thereof, such for instance as shown in Fig. 8, may be used with all of the modifications of the invention herein- 45 after described.

Referring to Fig. 3, 5| is a beam arrangedtosupport two weights 52, 53; the beam is rotatably mounted about an axis 55 parallel to the longitudinal axis of the shipand perpendicular to the 50 plane of the drawing by means of ball bearings 54. The axis 55 is supported by the casing on the upper part of which is fastened a spring 51 relieving the pressure from the bearing 54 due to the weight of the inertial elements 5|, latter is substantially immune from any friction.

The casing 56 is fixed to the support 60 supported relatively to the base 6| with interposed vibration absorbing material or element 63. The beam 5| of the inertial element is connected through-a rigid elastic link 63 to a comparatively strong fiat spring 65 fastened at the other end to the supporting plate 60. An oil dash pot 61 is connected to the spring 65 through a rigid elastic link 68. Another rigid elastic link 10 connects the inertial 65 element 5| to the amplification lever 1| pivotally mounted around the axis 12 and connected to the second amplification lever 13 pivotally mounted around the axis M. The lever system is counterweighted by means of the weights I5 and 16. On 7 the end of the lever 13 is mounted a plate 69 made, preferably of insulating material with two fiat coils 11, 18 made of a comparatively great number of turns of fine wire (see also Figs. 6 and '7). In view of the fact that the center of gravity of 52, 53, whereby the 55 the inertial element is on the supporting axis 55 the forces of inertia due to linear acceleration do not influence the inertial system and the latter is acted upon only by angular acceleration of rolling occurring about the axis parallel to the axis 55. The torque of inertia, as is known, being equal to the product of the moment of inertia of the inertial element 5| about the axis 55, times the angular acceleration, is absorbed by the spring 65 yielding by an amount proportional to the angular acceleration prevailing at any instant, and this deflection is amplified by the lever system 10, H, 13 and the vdeflection of the coils 11, 18 from the middle position is in this manner proportional to the instantaneous angular acceleration of the ship. ,Angular movement of coils 11, 18 about the axis of two A. C. electromagnets 19, energized by coils 8I, 82 shown also in plan on Fig. 6. Electromagnets 19, 80 are supported by a support slidably mounted between the guides 86, 81 for a slight linear movement up and down. In nor-' mal position, when no angular acceleration of rolling is acting the lever 13 is horizontal, as shown on Fig. 3 and the support 85 is in its middle position to which corresponds the symmetrical position of coils 11, 18, with respect to pole faces of the magnets shown on Fig. 6; alternating electromotive forces of equal amplitudes are induced in both coils 11, 18 in this case.

When in response to the angular acceleration of rolling the angular position of the coils 11, 18 is changed the number of flux linkages threading through the coils changes and the amplitudes of induced E. M. F. change accordingly. For example when angular acceleration to port (arrow 8|) develops, the spring 65 is pressed downwards by the link 84 and the coil end of lever 13 goes down also so that the flux linkages, and hence the induced voltage in the coil 18 increase whereas the corresponding values of the flux and induced voltage in the coil 11 decrease substantially in proportion to angular acceleration. It is to be understood that only small angular deviations oi lever 13 from the middle position are contemplated within such limits as will maintain the coils 11 and 18 in operative association with the magnets 19 and 80. To maintain the restricted travel it will be understood that adjustable stops 33 and 34 are suitably supported by brackets as shown, will be provided to sharply limit relative movements of the inertial element 5|. On the lower partthe sliding block 85 is connected to a rod 90, extending down to the interconnecting channel or pipe 4 and adapted for a small-linear displacement parallel to its length. The weight of the rod and the block 85 is preferably compensated by the upward push of a compression spring 9| pushing between the deck and a. shoulder 93 on the rod.

Inside the connecting channel is provided a stream line shaped body 92 suspended on levers 93, 94 arranged also in a stream line shape relative to the flow through channel 4, and pivoted about axes 95, 96 mounted inside a bell shaped extension 91 on the pipe 4. This is particularly valuable in connection with the indirect or impositive transference of water by the air pressure described, but in the event of positive or direct transfer as later described in connection with Fig.

11, different, possibly simpler means can be used.

The axis goes outside the extension 91 through a suitable stufling box 98 and is supported by bearing I00. A crank IOI fixed on the 14 takes place in the air gaps 1 ing deflection of springs I02, I03. The toothed placement substantially proportional to-the velocthat functional transformation.

' outside part of the shaft 95 is connected to two whose other end is connected to the shaft 95 near the crank IOI. The sleeve I04 is fastened to the toothed sector I06 counterweighted by the weight I01 and connected on the counterweight sideto 10 an oil dash pot I08 substantially as shown.

The sector I06 is in engagement with a smaller pinion. I09 fastened to a cam II 0 onwhich bears a. roller 4I located on the lower end of the rod 90. An arrangement of auxiliary lever H2 and 1;- spring H3 is provided to maintain the contactbetween the cam and the roller.

Responsive to the angular acceleration to port (arrow 8 I) the water flows in the connecting pipe in the direction shown (that is, to starboard) as 20 will be pointed out, the stream lined body 92 is dragged to the right until the torque due to skin friction of 92 is compensated by a correspondsector I06 moves up and the cam IIO turns clock- 25 wise into position which causes'lowering of the rod 90 with the magnets 19 and 80. For the flow in opposite direction opposite movement takes place and the electromagnets 19 and 80 are raised. The force acting on the body 92 generally varies as the square of the velocity of'the flow and in order to produce the up and down disity of water in the pipe or channel 4, the profile ot the cam must be chosen accordingly to effect 88 The body 92 even if madeon a stream line principle is liable to produce a turbulance in the now and be subjected to vibrations the arrangement of the elastic link constituted by spring I05 and dashpot 40 I09 eliminates vibration from the control segment I06 and permits transmission of a damped motion to the rod 90 substantially proportional to the velocity of the flow.

The arrangement shown on Fig. 3 constitutes a 45 follow up system between the angular acceleration of the ship registered by the inertialinstrument or accelerometer 5I and the velocity of the flow which permits of. obtaining a control of the type given by Equation (3) dw d e dt "dt erator, driven by a motor I I8. Generator II 5. is

connected to the pilot motor 50 in the so called Ward Leonard connection in which the armature I I1 of the generator is connected to the armature H8 of the motor and the field 9 of the motor is separately excited. Control of 'the speed of the motor 50 with associated valve control of the blower is accomplished byvarying the field of generator II1. A series brake I20 is provided on the shaft 48 of motor 50 with coil I2I in series in the circuit of armatures I I1, II 8. Generator II5 operates on the low value of its saturation curve so that the modification of resultant exciting am- 70' pere turns is characterized by a substantially proportional variation of the generated voltage. Q Generator I I5 has three differentially wound split fields I22, I23 and I24. The fields I22, I23 are 75- will now be described. Coils I1 and I8 are connected by one end to the cathode side of the thermionic system. Tubes or valves I32, I34 are adapted to work as amplifiers substantially on the rectilinear part of their characteristics by means of a suitable bias I35. Transformer coupling I42, I43 is shown to actuate the power tubes I30, I3I adapted to work as rectifiers by means of a suitable biasing electromotive force, shown as battery I44. Power tubes I36, I3I are connected to the differential split field I22 substantially as shown. Between the plates of tubes I36, I3I and the field I22 are inserted inductances of filter circuits I46, I65 forming with the associated capacities high frequency by pass smoothing out fluctuations of the rectified current. Between thefilters I46, I45 and thesplit field I22 are inserted the primaries of two high ratio transformers I36, I311. The secondaries of these transformers are connected to the negative terminal common to the thermionic tubes through a source of a suitable biasing electromotive force, not shown, the remaining ends of these secondaries are connected to the grids of the power tubes I38, I33 whose plates are connected to the split field I23 substantially as shown. The centra taps of the differential fields are connected to the common positive terminal of the thermionic system. The source of the voltage supply for the tubes is shown as a conventional B eliminator I40 connected across the terminals of a small alternating current generator I4I shown to be connected on the same shaft as the motor generator set H6, II6. The same generator I II energizes coils BI, 82 of electromagnets I9, 80. The negative end of the direct current supply I40 is connected to the common cathode connection of the thermionic system.

In addition of the follow up system between the movement of the coils 11, I8 of the accelerometer and the response of the flow reestablishing the equilibrium by bringing back the magnets I9, 86 in alignment with the coils through the intermediary of the rod 96 operated by the flow, there is a second follow up system on the follow up motor 56. To this end I provide an additional split field I24 connected to a resistor I25 arranged in parallel position to the shaft 68. A sliding contact I26 fixed mechanically to, but insulated electrically from, the traveling nut I21, establishes the contact with the resistor I25. Contact I26 and the central tap of the field I26 are connected to the supply of direct current I28, I29.

It is apparent that when the contact I26 moves towards the motor 50 more current fiows through the right half of the coil I26 and less through the left one and vice versa for the opposite motion of the contact I26.

The described arrangement should not be considered in a limiting sense as a number of various modifications of the invention is possible within the scope of the appended claims. Fig. 8 gives by way of another example a control system accomplishing substantially the same result as that shown on Figs. 3, 4, 5, 6 and 7, but in which a certain number of elements of electrical control are replaced by hydraulically operated elements.

Referring to Fig. 8, I56 represents a block of heavy metal such as iron, lead, or the like, suspended on a long spring II shown as broken away in the middle and supported by means of.a bracket I52, fastened to the port side of the ship I. In view of the fact that an exactly similar equipment is mounted on the starboard side of the vessel, the followingdesoription and the drawings re- 5 late only to the instrument and circuit's'relative to, or operatively associated with, the port side of the ship.

The block I50 is guided for a limited movement in a substantially vertical direction by means of 10. three pairs of antifriction rollers I53, I54, I55 supported by shafts perpendicular to the drawing and capable of rolling with only a slight friction on the machined parallel guiding surfaces I56, I51 of the guide bracket I58, fastened to the ship substantially as shown. .On the lower'part an oil damper I60 containing oil or other'damping viscous fluid is provided.

A bell shaped support I63 fastened to the. rod I59 supports on its lower end a ring I62. The container I66 is fastened to the ship and has in the center an axial tubular extension I68. ,The rod I56 passes through the tubular extension I66 and has fastened on its lower end the upper wall of a deformable vessel or bellows I65 the lower wall of which is suitably fixed to the ship. The bellows is comprised of a corrugated preferably cylindrical surface made of a resilient material such as steel, phosphor bronze, rubber, and the like. The bellows I65 communicates by so means of a tube I66 to aU shaped glass tube I67. The tube I6'I has in its lower part a small amount of mercury I68, in which is immersed a thin high resistance rod I69 similar to so called grid leaks used in radio circuits. It isknown 85 that the specific resistance of such rods per unit length can be made of any value depending on the thickness of the conducting coating or layer from a few ohms up to several megohms per inch, for instance. As a coating material such material should be used which mercury does not attack and in order to avoid the oxydation of the latter an inert gas such as argon for example may be sealed inside the bulb I'III which merges into and communicates with tube I61, and which at the same time may be used as a compression chamber I70 when the mercury level varies in the tube I68. All of the U tubes sub- 'sequently described have similar bulbs, preferably. From the preceding description it is apparent that when the ship undergoes angular acceleration 2 d t of rolling a proportional linear acceleration 11 x d t directed substantially along the axis of the rod '30 I59 takes place and the force of inertia I 1 71? where m is the mass of theblock, that is its 65 weight divided by g acceleration of gravity acts upon the deformable I63 determined 7,5-

by the height of the mercury. The resistor I69 is sealed through the glass and communicates with the terminal I12 and the mercury with another terminal "I also sealed through the glass. The variation of electrical resistance between the terminals I'll, I12 is thus proportional to the instantaneous angular acceleration of the ship. The diameter of U tube must be small enough to assure the desired sensitivity and not too small in order to avoid the phenomena of capillarity which might otherwise interfere with the performance of the instrument.

A similar U tube I13 communicates with a deformable container or bellows I14 similar to container I65. The force actuating the container I14 is derived from the drag exerted on the stream line body 92 placed inthe cross channel 4 as was extensively described in connection with Figures 3 and 4 and not shown in detail on Fig. 8 for this reason, as its function and arrangement is exactly similar.

A facsimile bellows I80 is operatively associated with the traveling nut I21 capable of axial motion along the shaft 48 of motor as shown in detail on Fig. 7. The operative association is shown to be established by means of a fork I8I having a fulcrum axis I82 and engaging stud I83 on the traveling nut. The opposite end I84 of lever I8I is connected to the bellows I80 by a link I85.

Bellows I80 is connected to U tube I90 similar to tube I10 and I13 previously described. Tubes I61, I13 and I90 and their associated resistance rods are connected electrically in series substantially as shown, and when the mercury levels vary the resistance of the whole circuitbetween the terminal "I on tube I61 and I9I on the rod of tube I90, is varied; this last mentioned resistance is connected in series with the condenser I92 connected across the primary of a transformer I15. The circuit containing the condenser I92, and the variable resistor formed by the three U tubes between the points I and I9I is closed on the source of A. C. supply across the terminals I16 and I11 and constitutes a phase shifting network operating two hot cathode grid controlled rectifiers I86, I81,

Fig. 8.

whose cathode heating elements are omitted on A transformer I18 is connected by its primary to the source of supply between the terminals I16, I11 and its secondary I19 is connected to the anodes of the rectifiers I86, I81. The secondary of the grid transformer I15 is connected to the grids of the rectifiers. The central tap on the secondary is connected to the central taps of the filament heating transformers (not shown) and thus is at the potential of the cathode, and

is connected directly to the terminal I94 of the The central tap on the secondary of'the transformer I18 is connected to the other terminal I93 of the direct current line. It is well known that the average output of such system of two wave rectifiers can be controlled by shifting the phase, of the grid voltage which is obtained by means of the variation of resistance between the points HI and I 9I of the circuit shown. Operative association of the controlling" system shown on Fig. 8 with other parts of electrical control of the blowers'is indicated on Fig. 9 in which the U shaped variable resistors are indicated diagrammatically as wire resistors. I

The circuit to the left of the terminals I93, I94 is the same as that shown on Fig. 8. A high 'of the ship are shown on Fig. 9 to act on the frequency by pass filter 26I formed by inductances and condensers is connected across the direct current terminals I93, I94 of the rectifier system in order to obtain a substantially constant and non-fluctuating output of the rectifiers. This output is passed through the primary of the transformer I36 of which the secondary is operatively associated with the tube I39 as was explained in connection with Fig. 7. The rectifiers operatively associated with the instruments of 1 the starboard side, not shown, are connected to the primary of the transformer I31 while its secondary is connected to the tube I 38 as previously explained. The differentially wound split field I23 of the tubes I38, I39 responsive to the 15 rate of angular acceleration 20 magnetic structure of a separate generator 250 driven by the shaft 48 of the main motor generator set II5, I I6 and the armature 252 of this generator 250 is shown to be connected in series with the armature II1 of the generator III. In the arrangement shown on Fig. 9 electromotive forces responsive respectively to angular acceleration (armature -I I 5) and to rate of angular acceleration (armature 252) are combined whereas in the arrangement shown on Fig. 10 the combination is effected on the ampere turns and not on the E. M. forces. Furthermore the responses of the double follow up system is incorporated as one component of the field I22 on Fig. 9 whereas in the arrangement shown on 35 Fig. 7 a separate field I24 is provided for one follow up system whereas the other rate of flow follow up is incorporated on the instrument side of the arrangement (rod 90 with associated magnets 19 and 80).

These widely different forms of controlling instruments and circuits have a substantially identical performance 'as is apparent from the foregoing description. I I

Comparing the arrangement shown on Fig. 8 with the previously described one shown with reference to the control derived from the accelerometer shown on Fig. 3 it is apparent that the accelerometer I50 shown on Fig. 8 responds not only to rolling but also to pitching and heaving of the ship or any combination of these motions which will cause a change inthe level of the mercury column I88 and thus will modify the amount of resistance between the points "I and I9I controlling the phase of the voltage impressed on the grids of rectifiers I86, I81 which will modify either the instant of their starting or in general their average output. It will be apparent, however, that exactly similar components of acceleration due to pitching or heaving will be .0 impressed on the second accelerometer (not shown) situated on the starboard side of the vessel which will cause substantially the same modification either in starting or in the average output of the corresponding rectifiers (not shown) operatively associated starboard accelerometer (not shown). It follows therefore, that although pitching or heaving or their combination will aifect the rectifiers operatively associated with the port and of the starboard side it 70' will afiect them equally and in the same direction so that the resultant effect of the differential split field due to these motions of pitching or heaving will be ml and by the same line of argument it will be readily understood that no resultant effect will be exerted on the magnetic structure of the auxiliary generator 250 responsive to the rate of acceleration of rolling. It follows therefore that the level of mercury in the tubes I13 and I90 will not be affected by pitching or heaving. From the foregoing description it is apparent that the system shown on Fig. 8 responds selectively to rolling when the accelerometers of the port (I50) and of the starboard (not shown) sides act additively in the control and is immune against pitching or heaving or any of their combinations, by virtue of the above described elimination of these disturbances in the differentially wound fields. It can also be clear that temperature variations which may modify the levels of mercury in the tubes I61, I13, I90 owing to the expansion of the inert gas in the bulbs of the tubes also cancel out their effects in the differential effects of oppositely wound fields of generator 5.

The preceding description relates to the control of the rate of the flow and of the acceleration of the flow in response toangular acceleration whereby the excess of water instantaneously concentrated on the rising side of the vessel at all times is made to be substantially proportional to the instantaneous angular velocity of the vessel. This concentration is obtained by the process of integration of the rate of the flow with respect to time. It is well known that in all methods or apparatus utilizing integration processes a cumulative error is possible. In this particular casev this "would mean that the liquid ballast may drift slowly to one side of the vessel. The simplest theoretical method of obviating this difiiculty would consist in introducing a directional control derived, for example, from a long period pendulum, as is disclosed in my co-pending patent application Ser. No. 544,651. In the instant invention it is preferred to produce equalization of the ballast from time to time by means of the control shown on Fig. 10, for the following reason. In view of the irregularity of the waves encountered periods of a relative quiescence occur from time to time as the records of rolling definitely show. These periods of quiescence are generally of short duration and are manifested as flat spots in the acceleration as well as in the rate of acceleration curves, that is, when these quantities continue to be small for a short interval of time as will be readily appreciated from an inspection of Fig. 14. No appreciable moment is transferred from the waves on the ship during such time intervals and the currents flowing in the branches of difierential fields I22, I23 of the generator are equal, or substantially equal, as will be clear from what has been explained previously. Referring to Fig. 10, 200 and 20l are two relays having each differentially wound field coils inserted respectively in series with the differential fields I22, I23 of the generator 5. Armatures 202, 203 of the relays when the relays are not energized close contacts of an auxiliary circuit as shown, I

206, 201 arranged to open From the above description it follows that whenever a point of quiescence develops both relays 200 and 20l are deenergized which energizes the solenods 20S'and 201 and opens the valves 200 and quiescence are utilized to eliminate automatically any cumulative excess of water which might occur in the long run as inevitable in the process of integration of the flow. 1

In the preceding description the control of the 10 stabilizing moment isproduced by the corresponding. control of the blower pressure applied to the water ballast whereby the latter undergoes displacements in accordance with Equation (2) both for regular and irregular rolling as will be shown in the following.

The invention, however, is considerably broader than this particular method of actuating these displacements and I wish it to be understood that any other possible method or means for producing the displacements of the liquid ballast in accordance with the above method can be adapted for the control of the type described. By way of another example Fig. 11 shows another displacement actuating mechanism operatively associated with similar controlling instruments and circuits which therefore gives substantially similar roll quenching characteristics, as the blowercontrol previously described.

Referring to this Fig. 11, 300 is a propeller or screw fitted into a flanged section of the cross channel 4 characterized as 3. The screw 300 is mounted on a shaft 30l supported by bearings 302, 303 made preferably of lignum vitae as commonly used in bearings of ship propellers and supported by suitable flanges or spiders 304, 305 of a preferably stream line cross section so as not to interfere with the flow of water through the channel 3| 1. The shaft'30l is passed through the channel 3 and emerges from inclined sec- 40 tions 3l9, 320 of channel 4 by means of bearv ings 306,301 mounted in the walls of the respective inclined sections 3l9, 320, which bearings serve also as stufiing boxes. The shaft 30l is connected directly to the shaft of a variable speed reversible hydraulic preferably oil motor 308 connected by means of oil lines 3l2, 3l3 to the variable delivery oil pump 3 driven by a constant speed electric motor, not shown, by a shaft perpendicular to the plane of the drawing. The control member 309 of the oilpump (shown as a conventional Hele Shaw pump) designated sometimes according to the type-of the pump as floating ring in the instant disclosure, tilting box" etc. in other types of pumps is adapted for I "a suitable design of the screw 300 and thecentral channel 3 the cavitation phenomena can be substantially eliminated. Furthermore the design of the screw must provide equal performance for opposite rotation of the shaft 30}; For given pitch, diameter and slip of the screw in a steady state condition the propeller 7o delivers a certain rate of .discharge'which is a definite function of these quantities. If the slip varies the momentum transferred-by the screw to the water in the channel 4 is varied, so that it is" possible by a suitable control of the slip 1:,

209 whereby these instants of o and hence of the speed of the shaft 30I to change the'rate of flow of the liquid ballast through the, channel 4.

It is apparent that the remaining parts of the controlling system remain substantially the same as previously described. For this reason they are indicated only diagrammatically on Fig. 11 omitting any such details as have been already described. The stream line body 92 with associated ports, shown in detail on Figs. 4 and 5 is shown on Fig. 11 The angular displacements of the body 92 under the influence of flow through a suitable functional transformation system such as cam IIO, Figs. 4 and 5, and intended to transform the proportionality to the square of velocity of the-fluid characterizing the reaction or drag of the fluid on the body 92 into a linear or proportional to the velocity law, is applied by means of a sprocket chain 320 to the rotor of a well known angle transmitting system 32I, 322 comprising a transmitting element 32I and a receiving element 322, said elements being constituted by electromagnetic devices with interconnected polyphase stators and single phase rotors closed on a source of alternating current supply (not shown). For the sake of simplicity the well known wiring diagram is omitted and the electromagnetic devices 32I, 322 are shown as connected by a single cable containing all necessary wires. This furnishes a remote control, if desired, for the potentiometer 326, although obviously this may be directly connected to the stream line'body 92, when no remote control is needed. The receiving element 322 is connected by means of a suitable connecter shown as a sprocket chain 324 to the arms 324, 325 insulated electrically from the rest of the apparatus, but

bearing on the potentiometer 326 connected to the direct current supply between two diametrically opposite points 321 and 328. The movable contacts 324 and 325 are connected across the field 32I of the generator II5 which field introduces a follow up action responsive to the rate of fiow, through the instrumentality of the stream lined body 92, synchronous angle transmitting system 32I, 322, if used, and the potentiometer 326. When there is no flow in the cross channel 4 and the stream line body 92 is in its central position the line of contacts 324. 325 is at right angles to the line 321, 328 on the potentiometer, and the contacts 324, 325 are at equal potential and no current flows through the field 32L Responsive to the velocity of the flow the contacts 324, 325-rotate-along the potentiometer in one direction or the other in proportion to, or as a certain function of, the rate of the flow through the channel 4 and the current through the follow up field 32I flows substantially in proportion to the rate of flow of the liquid ballast through the channel. The above mentioned functional transformation in another form, can be incorporated conveniently in the potentiometer design so as to have a suitably distributed resistance of the potentiometer for a given angle of rotation of the contacts 324, 325, so as to substantially effect this transformation electrically without any mechanical devices such as cam IIO, shown on Figs. 4 and 5.

Under these conditions the ampere turns of the follow up field 32l can be made substantially proportional to the rate of vflow of the liquid through the channel 4 both in direction and magnitude. The remaining parts of he scheme shown on Fig. 11 remain substantially the same so that these openings rise a worm wheel thread 401 as previously described in connection with Figs. 7, 8 and 9.

For instance the field I22 is connected in the circuit of the tubes or valves I32, I34, responsive to angular acceleration of the ship and the field I23 of the phase advancing generator 250 responsive to the rate of angular acceleration or to the third time derivative 2? of the ship's rolling is connected to the tubes I38, I 39 as previously described.

In the preceding disclosure the regulation of the direct or actual transfer of water between anti-rolling tanks through the cross channel 4 was described. It is known that in some instances the outboard anti-rolling tanks without any interconnecting channel 4 are used. Such outboard tanks are fitted with an opening or a series of openings communicating the tanks with the outboard water. When the ship rolls the openings, normally slightly above water line, s'ubmerge in the water and pick up a certain amount of outboard water which falls back into the sea when the vessel rolls in the opposite direction, above the average level of the sea. Such outboard tanks are very inefiicient, in view of wrong timing of filling and emptying, complicated by the phenomena of eifective orifice, dependence upon the speed of the vessel, form of the waves, to say nothing of their being'inoperative on a confused sea. The above described controlling system can be applied to improve the efliciency of such outboard tanks as will now be described. Referring to Fig. 12 representing the plan view of the port tank 399, 400 is the outboard opening (for which may be substituted a plurality of openings), into which is fitted a frame 40I, pivotally mounted for a limited angular displacement about an axis perpendicular to the normal water line of the ship, as shown also on Fig. 13. The pivotal axis 402 of the frame MI is supported by a step bearing 403 and by a guide bearing 404. The

shaft 402 extends upwards and emerges from the serves as an additional bearing. A sector 406 is fastened to the shaft 402. The sector 406 has engaging the worm 408 of the motor 50. The frame MI is thus capable of being rotated by the motor 50 over a certain angle about its middle position when with the outboard surface of ship I. The maximum angular movement is limited to a certain angle b on both sides of the central position; the

choice of the angle b is dictated by hydrodynamical consideration. The rotation of the frame 40I in'one or the other direction from the middle position introduces a scoop effect whereby the flow of water in, or'from, the tank into the sea can be somewhat controlled, as long as the opening remains submerged. The intake of water into the tank can be facilitated by the scoop action when the-frame 40I isin position a and the outflow of the water from the tank can be activated when it is in 0 position. The motor 50 may have a substantially similar control as previously described, butfrom the standpoint of the power rating it must be a'somewhat larger motor than the pilot motor 53 shown in preceding figures, as more power may be needed in this case. Owing to the possibility of controlling the flow of water into, or out of the tank when the opening is in the immersed position it is thus it is flush possible to improve somewhat the emciency of the outboard tanks by approaching their performance closer to the theoretically optimum. condition of roll quenching formulated by Equation (2). It is also apparent that both the blower method and the impeller method can also be used in conjunction with the controlling instruments and circuits for outboard tank control with the advantage-over the scoop method in that the control of the flow is not necessarily limited'to the periods of time when the opening 400 is in the state of immersion, as is inherent in the scoop method shown on Figs. 12 and 13.

The performance and operation of the stabilizing system will now be described. In view of the fact that the passive tank system ofiers a comparatively satisfactory roll quenching action when the waves are regular and when the conditions of a substantial resonance between the waves, ship and the tank are fulfilled, it is important to show that the controlling system forming the subject of this invention provides a satis iactory solution of the problem when the above mentioned conditions do not exist (as for instance when the waves are irregular), and when, consequently, the passive tank system fails to quench the rolling. Conversely, if the controlling system of the type described is capable of quenching the irregular rolling it is apparent that the regular synchronous rolling with the above specified conditions of resonance will be quenched e ipso and the system will .function at this particular point with a reduced call upon the external power, as will be shown.

The actual rolling, however, is practically. always irregular and the regular trochoidalrolling is a rare exception rather than the rule.

For this reason the" description of the performance in the following will be made with reforence to an essentially irregular or erratic rolling from which the advantages of this invention can be particularly well ascertained and appreciated.

Referring to Fig. 14 the curves on the upper part of the figure represent the conditions of a confused sea plotted against time as abscissa. More specifically curve a is the angle of roll actually observed on a vessel having a comparatively high metacentric height and subjected to a train of irregular waves.

Curve b is the slope curve for the curve a; it represents therefore the instantaneous angular velocity is df of rolling.

Curve c is the slope curve for the curve b and represents angular acceleration" Curves b, c and d are each-susceptible of double interpretation. One relative to the motion of the ship, and the other relative to that of the liquid ballast. These curves are plotted to diiferent scales (not indicated on Fig. 14) representing {or curve a (for example) degrees'on the axis of .of the abscissa axis. figures represent direction of flow through chanordinates, for curve b-degrees per second, for curve c-'-degrees per second, and finally for curve d-degrees per (second) The upper part of each curve (b, c, and (1) shown in dotted line relates to starboard relationships (e. g. angular velocity to starboard, etc.), while thelower part (full line) of the same curve relates to port relationship (e. g. angular velocity to port, etc.).

In view of the fact, however, that the timing of the water ballast must take place in accordance with Equations (2), (3) and (4), curve 1) represents also to a different scale the excess of .water in the tanks on the port side, when the angular velocity is to starboard (i. 'e. dotted part of the curve b) and on the starboard side when the angular velocity is to port (1. e.'full line part of curve b).

Likewise, curve 0 (angular acceleration di I of rolling) also may represent, to a different scale, the rate of flow of the ship, by virtue of Equation (4) may represent, to a suitable scale, the acceleration of the 35 flow in the channel 4 to port, when the rate of acceleration of the. ship is to starboard and to starboard when this rate of acceleration is to port.

On the lower part of Fig. 14 is diagrammatically represented a series of successive angular positions of the vessel at different instants of the irregular rolling, corresponding to the time scale Small arrows beneath the nel I, and by their length approximately indicate the magnitude of the velocity of flow at each instant. The arrows above the figures in a similar manner indicate the direction and approximately also themagnitude of angular velocity is (it of rolling. For the sake of clarity the angular deviations of the ship are greatly exaggerated and it is assumed that a residual irregular rolling exists of the same general. type as shown on the curves and that its presence is suflicient to actuate the instruments and circuits in such manner as to displace the water ballast in accordance withEquations (2), (3) and )4).

In order to be able to describe the operation it is necessary to assume initially that a certain condition of motion of the ship and of the ballast exists, and to ascertain that by the action of the stabilizer the displacements of the ballast are continuouslymaintaincd in accordance with the subsequent residual motion. whereby the operativeness of the stabilizer thus will be demonstrated.

Such description is, of course, only a partial one insofar as the residual motion assumed here as given in advance in reality is the result of operation .of the stabilizer. The completesolution l5 of the problem requires solution of the system of two differential equations, one relative to the ship and the other to the bal1ast,with suitable terms characterizing the coupling between these two systems and is irrelevant to the description of the invention proper.

For this reason an approximate description of performance of the stabilizer proper, assuming the existence of a certain irregularresidual rolling characterized by curves a, b, c and d, is given below. i

The theoretical conditions set forth by Equations (2), (3) and (4) are as follows:

Equation (2):

excess of water 10 must be situated at all times on the rising side of the vessel and must be varied continuously so as to be substantially proportional to the instaneou's angular velocity Q dt of rolling.

Equation (3) the rate of transfer T: of water and, consequently, the velocity of flow in the cross channel 4 must be substantially proportional at any instant to the angular acceleration 'of the ship and must be directed in the direction opposite to that in which this angular acceleration is taking place-which accounts for the minus sign in this and other formulae.

Equation (4) flow to port is a maximum. The description is made with reference to the arrangement shown on Figs. 3, 4, 5, 7 although the following description is equally applicable to Fig. 11. At the initial instant I the coil end of lever I3 (Figs. 3 and 7) is moved upwards in view of the acceleration to starboard at this instant. The amplitude cf E. M. F. induced in the coil 'I'I increases and that in the coil I8 decreases, which unbalances.

the thermionic push pull system of the tubes I39, I3I in the manner previously described. The follow up motor 50 starts to run through a number of revolutions proportional to the magnitude of the unbalanping and hence in proportion to the magnitude of angular acceleration at this instant I until the compensating action of the field I24 regulated by the contact I26 moved along the resistor I25 stops it. The blower output is thus directed more to the starboard tank than to the port one and the flow of water develops in channel 4 from starboard to port gradually increasing the level of water in the port tank substantially in proportion to the increase of angular velocity (curve 0) of the vessel to starboard. As a result of the flow the-stream line body 9: (Fig.3) is de- 5 'viate'd to port to the left on Fig. 3 which raises the appearing unbalanced condition the follow up mo-,

tor starts in the opposite direction seeking the new point of equilibrium, which reduces the output of the blower on the starboard tank and decreases the velocity of the flow' to port. The water in the 15 port tank risesbut the rate of this rise gradually decreases with the approach to the instant II. During this period the inductive coupling by means of transformers I36, I 31, whose secondary induced voltages are substantially proportional 20 to the third time derivative of angular motion of the ship, in view of the arrangement disclosed, reduces the field of the generator II5 by operating on the grids of tubes I38, I39 and thus modifying the ampere turns of the auxiliary split field I23 so 25 as to advance the instant at which the blower pressure on the starboard tank is reduced and also .to advance the instant at which the cushioning counter pressure on the port tank is applied, whereby the reversal of the flow at the instant II 30 is facilitated. The action of the inductive coupling responsive to the third'time derivative is thus to produce an easing off" action of the blower, which reverses its action slightly ahead of the theoretical instant of reversal in order to take into account the inertia of the moving water. At instant II the ship passes through the even keel 40 condition with no flow in channel 4 and with the angular velocity to starboard just slightly past its maximum value. The excess amount of water concentrated in the port tank is substantially proportional to the magnitude of angular velocity at this instant in accordance with the optimum damping condition expressed by Equation (2) Referring now to the time interval II-III it is seen that the angular acceleration to port (which is clearly equivalent to the rate of decrease of angular velocity to starboard) is gradually increasing. The spring 65 (Fig. 3) is pressed down and the coil end of the lever I3 is moved down accordingly. The amplitude of the E. M. F. induced in the coil". is now increasing; that of 55 the E. M. F. induced in the coil I? is decreasing, which unbalances the thermionic push pull system of power tubes I30, I3I in the direction opposite to that which was previously described in relation to the time interval III. The blower 60 pressure is directed now more into the port tank, increasing the rate of the flow to starboard up to a maximum, approximately in the middle of the interval and then reducing it again (instant III). The performance of the double follow up system 65 is exactly the same as before and does not need to be repeated. During the first half of the interval IIIII the valves or tubes I38, I39 operated in response to plate current variation of the valves I32, I34 introduce additional ampere turns 70 in the split field I23 which accounts for an ad-' vance in the application of the pressure to the port tank, which leads or precedes an analogous action exerted by the valves I32, I34. The valves I38, I39 thus exert a mee'ing action as far as I reduced between the points P and Q,

the acceleration of the flow of water to starboard is concerned. It is tobe noted that this acceleration is somewhat facilitated by the fact that the water is accelerated downhill in view of the fact that the ship is inclined to starboard during this period. During the second half of the interval II-III the valves I38, I39 again exert an easing off effect whereby the velocity of the fiow to starboard is gradually reduced. The time interval III-IV characterizes particularly well the irregularity of the disturbing moment applied by the wave slope to the ship. The earliest fore-runner or anticipating factor of. the irregularity appearing between III-IV appears substantially around the point 111, in the fact that the curve at ceases to increase as rapidly as it should if following along line A-B and begins to decrease shortly after point III. The easing ofi action exerted by the valves I33, I39; instead of being continued after the point IE as would be the case of a regular rolling, is which is transmitted againthrough the instrumentality of the valves I38, I39 and the differential field I23 so that the velocity of the flow instead of following the variation substantially along line LMN of the diagram, that is, reversing to port at a the point M, is reversed only at the point 3 and in accordance with thus matches the development of a "flat spot" in the acceleration curve in the region between the points M-S-T.

' In the case of a passive tank system the velocity of the flow in the channel 4 would follow line LMN instead of following line LSR and for this reason the useful action of the passive system would be lost at'the point L and such passive tank system would become inoperative .and indeed would exaggerate or enhance that condition it is designed to correct. The velocity of the flow temporarily delayed by the anticipatory control of they valves I 38,. I39 in the regionbetween the points M-T will be again increased and the -more or lss regular character of the impressed disturbing torque of the sea will appear after the instant IV and the various phases of controlling actions can easily be analyzed further in the manner in which the analysis was applied to the time interval I---1I--III--IV.

The controlling action exerted by the instru ments on the flow of the water will be at all times region between the curves re fit depending on the relative importance of the angular acceleration control (tubes or valves I30, I 3|) and the rate-of angular acceleration control (tubes or valves I38, I39) If the former is predominant/the blower action will be directed more the angular acceleration 91 an (curve c) whereas in case of the predominanc of the latter this blower action will approach represented by a curve (not shown) lying in the and ' nearer the'curve :1 representing the rate of angular acceleration This change in the character 01 the resultant v performance extended control can be accomplished for example by shunting the fields by. means of variable resistors 2H), 2H, shunting the field I22 (Fig. 9) or by means of a variable ratio of transformation I8, 80 whereby the coupling coefiicient a can be I suitably changed so as to adjust the performance to suit the conditions. I I These various adjustments and regulations together with the continuity of actions exerted by thermionic systems permit a close following of the disturbance by means of the water ballast concentrated at all times on the rising'side of the vessel so that the amount of the excess ballast remains substantially proportional to the instantaneous angular velocity of the ship at this instant, whereby the potential energy of the disturbing wave slope is consumed in a continuous raising ofthe extra ing remains quenchedvboth for regular or irregular waves. I

The analysis of the performance for the regular rolling follows the same line of argument as weight of water and the rollwas applied in connection with the part I-II stabilizer of the type to the case of a passive and not to the potential head arisin g from the angle of rolling as in case of a passive system. In other words, the ship does not need to rollover appreciable angles in order to produce its stabilization which is clearly a mutually excluding condition explaining the low roll quenching efficiency of the passive tank system.

In order to emphasize this important feature the description of the performance is made with reference to Fig. 15. The curves 'on the upper part of, Fig; 15 are the same as corresponding .curves of Fig.14. Inview of the assumed regu-' larity of rolling the analysis is limited only to one half cycle or period since during the other half cycle the conditions are symmetrical and it is suificient in the following description to substitute the word starboard and vice versa in order to have the analysis of tothe second half period. On the lower part five subsequent positions of the ship corresponding to the. instants I, II, III, IV, V of the upper curves are shown. 3

Referring toFig. 15, during the time interval II[, the angle 9 to starboard gradual y increases and angular velocity i dt of rolling to starboard decreases. This time interval thus corresponds to the beginning of. the time interval 11-111 of Fig. 15 with respect to for the word portj a the pilot motor 58 in the corresponding which the behavior of instruments has been already described. Angular acceleration to port the inertial instrument or accelerometer will gradually increase the degree of unbalance of the themiionic system of the tubes I30, |3l operatively associated therewith which will start direction so as to increase the rate of delivery of oil by the pump 8 I4 and increase the rate of rotation of the hydraulic motor 308 so as to increase the positive slip of the screw 38!) to the extent at which the acceleration of water to starboard in the connecting channel is built up so as to produce a velocity of the fiow satisfying the theoretical relation (3), at this instant the stream line shaped body through its associated potentiometer control reduces or even reverses the excitation of the generator H5 through the follow up field 82| which will finally react through the instrumentality of the hydraulic transmitting system 8, 388 on the corresponding reduction of the slip of the screw 80!! whereby the latter will not accelerate the water any more. In reality the above described following up the given value of angular acceleration sive through the instrumentality of the tubes I88, I38 to the third time derivative as of rolling (curve d) whereby all the actions above referred to are slightly advanced so as to permit a continuous adiustment of the rate' of transfer of water to be substantially in phase with, the angular acceleration (Equations (2) and (3)) to be continuously fulfilled.

During the time interval lI-III the velocity of the flow of the liquid to starboard gradually increases and is maximum at the instant III when the ship is at the extreme starboard swing and when its angular velocity is zero. The gradually increasing acceleration of water to starboard during the time interval I-III, as is apparent, is mainly attributable to the external source of power (motor driving the oil pump 3), which through the instrumentality of a suitably controlled slip of the screw 800 is impressed upon the water in the cross channel accelerating it to starboard. For.this reason considerable displacements of the water ballast necessaryfor an emcient stabilization can be produced for appreciably smaller angles of rolling (i. e. for small values of. potential heads available) than those greater angles which must necessarily occur if the passive method is to function. For the sake of a qualitative comparison the corresponding position of the vessel in this latter case is shown in dotted lines.

Similar analysis can be applied to the time interval III-V when .the angular acceleration to port decreases and when, consequently, the slip of the impeller 80!! from positive will become negative, which will cause the deceleration of the moving fluid. During thisperiod a partial regeneration of energy will take place and the external source of power will absorb less energy since a part of the energy will be restored from the loss of momentum of the decelerating water obtained through the instrumentality of the negative slip of the impeller 800 controlled in response to the decreasing acceleration to port.

The starting or stopping of the operation of the stabilizing system can be accomplished in any manner in which the coupling coefficient a appearing in Equations (2), (3) and (4) can be varied. This can be accomplished for example by changing the filament temperature, and hence the thermionic emission of vacuum tubes, by shunting or by-passing various field windings, such as, I22, I23 (Figs. 7 and 9), controlling the excitation of generator I It, by changing the speed of the motor generator set by changing the resistance I49 in series with the coils 8 I, 82 of magnets shown on Fig. 7, whereby the amount of modulation by the coils TI, 18 is changed, or by any other well known either electrical or mechanical means, by which the operative association designated for the sake of abbreviation as coupling coeilicient "a, between the displacement :0, rate of displacement d t and acceleration of displacement I dt' v of the liquid ballast on one hand, and angular velocity dt angular acceleration 11 9 d t and the rate of angular acceleration F of rolling onthe other hand, can be varied. For example, at starting the coupling coefficient a will be slowly increased from a substantially negligiblevalue by gradually decreasing the resistance of the rheostat I48. The water ballast will start moving between the tanks with gradually increasing average velocities per cycle (with decrease of resistance) whereby more and more differential excess water w will be introduced into the process of stabilization and the rolling of the ship will be gradually reduced until a steady state condition will be reached, corresponding to the maximum value of the coupling coeilicient' a at which full amounts of the transferred water will be rushed back and forth be- 

